What is the proper way to use solid boosters?

[kurja]

I like to use solid boosters for, well, boosting, doubling as drop tanks; I put liquid fuel on top of them so that by the time SRB's come off the main engine tanks are still more or less full. I haven't seen many rockets around here that would use this, maybe there's a drawback that I haven't realized?

[Virtualgenius]

SRB's are designed to give you the kick to a higher altitude carrying a decent velocity also, where the drag is less and the air is thinner and where your main engines perform better and they push you into orbit. I use them all the time when the game puts costing on a launch srbs are recoverable there cost will be low to reuse

[FenrirWolf]

They're good for giving you a 'free' boost in the first stage of your rockets. Not completely free of course since they add weight to the rocket, but they don't burn your normal fuel and when you're done with them you just get rid of them.

Also, the introduction of thrust limiting makes them much more useful than before. Lets you burn them longer and not kick quite so hard when the atmosphere is at its thickest

Edited March 16, 2014 by FenrirWolf

[federally]

The main reason to use SRBs is the awesome smoke cloud they leave in their wake.

[Accelerando]

The main reason to use SRBs is the awesome smoke cloud they leave in their wake.

Yes. They're easy to tack on, too, and make small things go fast.

[magnemoe]

They're good for giving you a 'free' boost in the first stage of your rockets. Not completely free of course since they add weight to the rocket, but they don't burn your normal fuel and when you're done with them you just get rid of them.

Also, the introduction of thrust limiting makes them much more useful than before. Lets you burn them longer and not kick quite so hard when the atmosphere is at its thickest

Smart, never thought of that one.

Yesterday I used SRB as in the trashcans on stage two in an 3 stage asparagus. second stage had too low TWR and the simple solution was to slap on four trashcans. who fired then the first stage was dropped, this let me keep an TWR of 1.6 trough both first and second stage. 3rd stage had only 1 TWR but at that time i was traveling with more than 1 km/s.

[Dispatcher]

When money becomes a thing, asparagus is going to be seen as the false prophet, and boosters are going to be seen as the road to the future, considering that you only have 1 part for a booster, versus the 40 or so parts that go into asparagusing, a fourth of which are the motors themselves which are a bit spendy iirc.

For heavy transfer stages (not launch stages) I use an asparagus setup; not with engines, but with fuel tanks. Reduced TWR is not a problem in this case.

SRBs are excellent for the reasons you mentioned. Also, their diameter allows them to fit radially between larger diameter parts, making for a reasonably compact footprint. Sure, the same thing is true of the 1.25 diameter liquid fueled parts, but then the advantages you mentioned come into play again.

[wilt57]

When money becomes a thing, asparagus is going to be seen as the false prophet, and boosters are going to be seen as the road to the future, considering that you only have 1 part for a booster, versus the 40 or so parts that go into asparagusing, a fourth of which are the motors themselves which are a bit spendy iirc.

I agree SRBs will have a stronger future when costs come to play, but I don't think asparagus will be any type of false prophet. IMVHO, one should never include SRBs with the intention of adding delta-v to a rocket. The best use of SRBs is adding TWR to a rocket that has the delta-v to make orbit, but loses too much to gravity due to too low a TWR. Here, the SRBs are not adding delta-v, but recovering lost delta-v. Tweakables help here quite a bit, as I've always felt the current SRBs have too short a burn time.

It's nice that an SRB comes with fuel and engine all in one part and thus helps lower part count, but if you are up against part count limitations, I don't think a 325 kN engine is going to give you the increase in thrust you need for that monster. Perhaps the inclusion of a 2.5m SRB would, but not the current 1.25m parts.

This is all concerning the launch vehicle. Once in orbit things change quite a bit.

[Random Tank]

I think a better question would be: Why wouldn't you use SRBs?

As a couple of people before have said, all they are meant for is boosting the main launch stage to a higher altitude; think launching off a mountain.

With the lack of thrust control, different fuel usage and static fuel amount, they are literally designed to be the first stage of a rocket. Some people are looking are looking at SRBs completely the wrong way; they aren't designed to replace your Mainsails, but assist them!

Plus, others say that SRBs add weight to a ship; well, because the thrust, burn time, fuel capacity and weight are always a static figure, they will never actually weigh a ship down during burn time, and you drop them once they've finished. So apart from increased part count, they have no downside! I use SRBs (usualy BACCs or KW SRBs) on every rocket I launch, because simply, why wouldn't you?

[MedwedianPresident]

I think that SRB's play a major role in KSP since they can launch small objects into escape trajectories. I often use a large SRB as a first stage for my rocket.

[Endersmens]

Once i used them in a unique way. I had a 2.5 meter mun lander, so i built a big KW rocket under it. for the mun transfer stage, i didn't feel like just using the regular stage. so i slapped 24 of the small KW SRBs that burn for 30 seconds. they gave me an almost perfect (within 50 m/s) transfer burn without using any of my regular transfer stage. ended up dumping tons of extra fuel to smash into the mun, but hey. the next mission had 2 less stages. i wouldn't recommend this method unless you do some calculations for you estimated burn delta-v requirement and the delta-v the srbs give you cause you cant shut them down. so if you overshoot you have to burn a little extra fuel to correct.

[Amaroq]

One of my favorite uses of SRB's has been to calculate the burn time I can expect from a given liquid fuel tank/engine setup, and then couple the SRB's with the matching burn time to them. This is useful if my build has reached a good dV but insufficient TWR ..

In practice, I tend to be close on TWR already, so I select an SRB with a longer burn time, as then I can throttle-down the liquid ... net result is, the same upper stage decouples at a higher altitude, done.

For example, I've a 6X asparagus-build which uses the radial-mounted KW "Globe" SRB's, staggered such that the shortest-burn SRB's are on the first asparagus-pair to drop, with the middle-duration on the second pair to drop, and the long-duration SRB's on the final pair. Its a bit of a hell-beast to control on the way up, but it worked out pretty well.

[AlamoVampire]

all of the below, made possible by the use of SRBs.

[Red Iron Crown]

all of the below, made possible by the use of SRBs.

http://imageshack.com/a/img534/7227/m4z2.png

http://i.imgur.com/uhP0Rto.png

http://i.imgur.com/mwCcmjN.png

SRBs may have made launching those easier, or faster to build, but they didn't make them possible. Liquid fueled boosters would've gotten them up just as well.

For me, SRBs don't make sense until we start taking cost into effect, so in the current game I don't use them. That is likely to change when economics are introduced.

[Claw]

I try not to get too hung up on the "it isn't the most optimum piece." I use what feels natural for me for that design. It's an open ended game. You don't have to eek out every drop of dV unless that's your goal.

SRBs exist for real because they are less complex, relatively light, and can be strapped to existing rocket designs to boost payload. None of these are limitations in game yet, so it's mostly up to your play style.

So if you have a rocket that is Mun capable, but you want to take a bit more science with you on the second flight, an SRB may be an easy fix. Sure, there are lots of ways to "fix" the design with liquid rockets, jet engines, more fuel, etc. SRBs are simply another option.

[Guest]

SRBs are great if your TWR is too low. IRL, the main reason to use boosters is when you have enough (or a few hundred m/s short) dV to get into orbit you want, but the main engine TWR is below 1. Adding boosters mitigates that. In general, boosters for low TWR, upper stages for low dV. Keep iterating until you've got enough of both, or the rocket turns into a mess (in which case, scrap it and use a different core LV).

[Othuyeg]

A massive space plane can benefit from a SRB. Sometimes getting the speed up on the runway can be difficult in massive planes using just jet engines. However, balancing them in planes is very difficult.

[AlamoVampire]

SRBs may have made launching those easier, or faster to build, but they didn't make them possible. Liquid fueled boosters would've gotten them up just as well.

For me, SRBs don't make sense until we start taking cost into effect, so in the current game I don't use them. That is likely to change when economics are introduced.

SRBs are a better bet over liquid for a boost stage. Plus some of those in the picture tipped past 1 kilo ton on the pad, especially that station. I got away with more power AND less parts on those ships with SRBs

[KerbMav]

Under DRE the use is tricky at times. The high thrust and acceleration in the thick lower atmosphere (even with FAR) crunches/burns my rockets from time to time.

The lack of gimble calls for a liquid engine to burn at the same time, adding to the thrust.

Being able to lower the thrust and amount of fuel helps a lot and has proven to be a wonderful addition to the stock game.

Yet as the TWR increases while the fuel is burned and the drag decreases, finding the sweet spot for tweaking to not get to much acceleration in the last seconds the solid boosters are burning is still a challenge to me.

[wolfedg]

This like so many others is my opinion, but SRB's were how I made my first sucessful Mun landing and the workhorse of my Kerbin SOI operations.

The SRB's on this Quest 5 make it possible to keep the craft size relatively small and still have very close to 2 full stages left after achieving LKO.

And yes I used a Poodle engine for the 3rd stage =.

[cantab]

A massive space plane can benefit from a SRB. Sometimes getting the speed up on the runway can be difficult in massive planes using just jet engines. However, balancing them in planes is very difficult.

In other words, a JATO. It's an approach that also works well on rovers .

[thereaverofdarkness]

Solid boosters are more efficient than liquid engines. They would be better for lifter stages if there was a 2.5 meter SRB. I use SRBs profusely when I haven't unlocked Skippers or Mainsails yet.

[Othuyeg]

In other words, a JATO. It's an approach that also works well on rovers .

Yep. Here is a video of me playing around with a concept inspired by the U.S Operation Credible Sport.

What was Credible Sport?

How did my attempt go:

http://www.twitch.tv/othuyeg/c/3868521

It was a part of a challenge on the challenge forums. Forgive me from the laggy video. I don't have good streaming system.